Idea Summary
Warn on unsaved changes doesn't work for modal dialog pages. It's even in the online help:
Note: This does not apply to an end user closing a Modal dialog page.
This is very inconsistent. It should also work for modal dialogs. Right now you have to program your own DA, but with an inconsistent UI:
https://community.oracle.com/tech/developers/discussion/4279421/warn-on-unsaved-changes-and-modal-dialogs
Related:
The X in the upper right corner doesn't fire the Close or Cancel Dialog event. Even with a Cancel or Back button on the page, users will still click on the X. There should be an option to add the Close or Cancel event to the X.
Use Case
UI consistency between normal and modal pages. Reduce user error.